1. Field of the Invention
The present invention relates to an auto document feeder and an image forming apparatus.
2. Description of the Related Art
Conventionally, apparatuses equipped with various driving systems have disadvantages in that noise, such as drive noise, generated inside the apparatuses may be leaked and disturb the environment.
Furthermore, if openings are formed on main bodies of the apparatuses, a shielding member that opens and closes the openings as needed is generally provided in order to prevent noise generated inside the apparatuses from being leaked from the opening.
However, in sheet conveying apparatuses, such as an auto document feeder (ADF), that sequentially feed and discharge sheets, it is difficult to shield a feed opening and a discharge opening, from which noise inside the apparatuses is leaked, while the apparatuses are running.
This is because, in a configuration in which an outlet is shielded by a discharge shielding member in a normal state and the discharge shielding member is rotated to open the outlet by a conveying force of a sheet being conveyed, it is difficult to cope with thin papers or the like. Furthermore, the stackability is not adequate.
Moreover, it may be possible to shield the outlet by the discharge shielding member in a normal state and open the outlet based on a detection result obtained by a detecting means disposed in a conveying path. However, in this case, a time lag occurs before the shielding member is opened. In this case, it may be possible that the shielding member may not be opened when a sheet reaches the outlet and such a configuration is not practical.
To cope with the above disadvantages, a sheet conveying apparatus has been proposed, in which a shielding member for shielding a feed opening moves according to the number of sheets stacked on a feed tray (see, for example, Japanese Patent Application Laid-open No. 11-334920).
According to the sheet conveying apparatus, the shielding member moves according to the number of sheets stacked on the feed tray, so that the shielding member can move to an appropriate position and shield the feed opening. Therefore, it is possible to prevent leakage of noise from the feed opening.
However, in the sheet conveying apparatus described in Japanese Patent Application Laid-open No. 11-334920, the shielding member moves to a position close to the sheet at the time of sheet feeding. Therefore, a space between the shielding member and the sheet is narrow and the operability of user's operation for, for example, pushing the sheet by his/her finger at the time of sheet feeding is reduced.
Therefore, it is desirable to improve a noise insulation effect by shielding the feed opening and to improve the operability of user's feed operation.